Ink jet head

Abstract

In an ink jet head, in order to make the occupying area of a chamber associated to each nozzle as small as possible, while maintaining a discharge ink drop volume, and on the other hand, to locate a number of nozzles with a high density, the plan view shape of a pressure plate provided to each chamber is so configured to fulfill the relation of 1:≦A≦2, where “A” is the ratio of an circumscribed circle diameter of the plan view shape of the pressure plate to an inscribed circle diameter of the plan view shape of the pressure plate. For example, the pressure plate is formed to have the plan view shape of a substantial square or a substantial rhombus. The chambers having such a feature are located in the form of a matrix. Thus, a stably driven, highly reliable ink jet head can be realized.

What is claimed is:  
     
       1. An ink jet head comprising: 
       a plurality of nozzles arranged to form a matrix having a plurality of rows inclined at a constant angle to a head main scan direction and a plurality of columns orthogonal to said head main scan direction;  
       a plurality of chambers provided for said plurality of nozzles, respectively;  
       a pressure plate formed to constitute one plane of each of said plurality of chambers;  
       an actuator provided to each pressure plate, for deforming said pressure plate to compress an ink within a corresponding chamber;  
       a plurality of ink pool branches provided along said plurality of rows or said plurality of columns, for supplying said ink to said plurality of chambers; and  
       a main ink pool connected to said plurality of ink pool branches,  
       wherein said pressure plate has a plan view shape fulfilling the relation of 1≦A≦2 where “A” is the ratio of a circumscribed circle diameter of the plan view shape of said pressure plate to an inscribed circle diameter of the plan view shape of said pressure plate.  
     
     
       2. An ink jet head claimed in  claim 1  wherein said pressure plate has the plan view shape of a substantial square. 
     
     
       3. An ink jet head claimed in  claim 2  wherein when the inclination of each row to said head main scan direction is expressed by “θ” and the interval of said plurality of nozzles in a direction orthogonal to said head main scan direction is expressed by “d” (mm), “θ” and “d” have the relation of 0≦tan θ≦5d. 
     
     
       4. An ink jet head claimed in  claim 3  wherein when the number of said nozzles included in each row is expressed by “n”, “n” and “d” have the relation of n×d≧0.2. 
     
     
       5. An ink jet head claimed in  claim 4  wherein “n” and “θ” have the relation of 0.5≦n×tan θ≦2. 
     
     
       6. An ink jet bead claimed in  claim 5  wherein said main ink pool has the cross-sectional area larger than the cross-sectional area of said ink pool branch. 
     
     
       7. An ink jet head claimed in  claim 6  wherein at least one of said main ink pool and said each ink pool branch has the cross-sectional area gradually decreasing toward the downstream end. 
     
     
       8. An ink jet head claimed in  claim 1  wherein said pressure plate has the plan view shape of a substantial rhombus having a pair of sides in parallel to said plurality of rows and another pair of sides in parallel to said plurality of columns. 
     
     
       9. An ink jet head claimed in  claim 8  wherein said actuator has a plan view shape of a substantial rhombus having a pair of sides in parallel to said plurality of rows and another pair of sides in parallel to said plurality 
     
     
       10. An ink jet head claimed in  claim 9  wherein each of said plurality of chambers has an ink supply port to form an ink flow in the direction of a long diagonal of said substantial rhombus. 
     
     
       11. An ink jet head claimed in  claim 10  wherein when the inclination of each row to said head main scan direction is expressed by q; i” and the interval of said plurality of nozzles in a direction orthogonal to said head main scan direction is expressed by “d” (mm), “O” and “d”  have the relation of 0≦tan θ≦5d. 
     
     
       12. An ink jet head claimed in  claim 11  wherein when the number of said nozzles included in each row is expressed by “n”, “n” and “d” have the relation of n×d 0.2. 
     
     
       13. An ink jet head claimed in  claim 12  wherein “n” and “θ” have the relation of 0.5≦n×tan θ≦2. 
     
     
       14. An ink jet head claimed in  claim 13  wherein said main ink pool has the cross-sectional area larger than the cross-sectional area of said ink pool branch. 
     
     
       15. An ink jet head claimed in  claim 14  wherein at least o we of said main ink pool and said each ink pool branch has the cross-sectional area gradually decreasing toward the downstream end. 
     
     
       16. An ink jet head claimed in  claim 8  wherein when the inclination of each row to said head main scan direction is expressed by “E” and the interval of said plurality of nozzles in a direction orthogonal to said head main scan direction is expressed by “d” (mm), “θ” and “d” have the relation of 0≦tan θ≦5d. 
     
     
       17. An ink jet head claimed in  claim 16  wherein when the lumber of said nozzles included in each row is expressed by “n”, “n” and “d” have the relation of n×d ≧0.2. 
     
     
       18. An ink jet head claimed in  claim 17  wherein “n” and “θ” have the relation of 0.5≦n×tan θ≦2. 
     
     
       19. An ink jet head claimed in  claim 18  wherein said main ink pool has the cross-sectional area larger than the cross-sectional area of said ink pool branch. 
     
     
       20. An ink jet head claimed in  claim 19  wherein at least one of said main ink pool and said each ink pool branch has the cross-sectional area gradually decreasing toward the downstream end.